The present invention relates to a miniature portable radio communication apparatus such as a paging receiver and, more particularly, to a watch type paging receiver which may be put on person's wrist by a belt.
In a miniature portable radio communication apparatus, a sufficient space is not available for an antenna because the casing of such an apparatus should be small enough to enhance portability. It has therefore been customary to use a loop antenna, ferrite antenna or like built-in antenna which has a highest possible antenna gain despite its miniature configuration and is hardly affected by a circuit board and others of the apparatus. Recently, however, the limitations on the position, size and shape of such a prior art built-in antenna have become much severer to meet the demand for further miniaturization of a radio communication apparatus, i.e. a small and thin apparatus casing. In such a situation, it is difficult to insure an antenna gain which is sufficiently high for usual reception.
Another problem with the prior art built-in antenna is that it is apt to electromagnetically couple with a circuit board, conductors and the like which surround it, failing to exhibit an expected antenna characteristic. When an antenna is installed together with a display section implemented by a liquid crystal display (LCD) device, for example, and a circuit board in the small and thin casing of a watch type paging receiver or similar portable radio communication apparatus which may be put on user's wrist by a belt, the characteristic of the antenna is necessarily degraded due to electromagnetic influence of the LCD device and circuit board. Eventually, a suitable space for accommodating the built-in antenna becomes unavailable.
An implementation for solving the above problem may be using the belt of the watch type paging receiver for an antenna. The belt may serve as a far larger antenna than the previously discussed built-in antenna and therefore achieves a high antenna gain. However, this brings about another problem because the length of the belt depends upon the person who uses the paging receiver. Specifically, should the length of the belt, or antenna, be changed, a matching circuit interposed between the antenna and a receiving circuit of the receiver will fail to establish accurate matching between the antenna and the receiving circuit.
Generally, a watch type paging receiver is provided with alerting means for alerting the user to the reception of a call. The alerting means may be in the form of a loudspeaker or an LCD device, a light emitting diode (LED) device or similar visual alerting means. Also known in the art is alerting means which uses vibration, i.e. tactual alerting means. This kind of alerting means is mainly applied to paging receivers of the type being carried in a pocket or on a waist belt and with which the space requirement is not so severe. The tactual alerting means has a vibration source which is bodily received in the receiver body so as to cause the entire receiver into vibration. However, using this kind of alerting means with a watch type paging receiver has hitherto been impractical because of the limited space available in such a receiver. More specifically, applying the tactual means to a watch type paging receiver will bring about the following problems.
(1) A single casing has to accommodate both of the receiver body and the vibration source and, yet, has to be as small as a watch, rendering the design extremely difficult. PA1 (2) When the receiver body and the vibration source are installed in a single casing, the casing itself is heaviest and therefore cannot vibrate unless the vibration source has considerable power.
A prior art paging receiver to be carried in a pocket or on a waist belt is powered by a manganese dry cell which is relatively large size (e.g. AA: 7.34 cc or AAA: 3.85 cc). This kind of dry cell is available with ease and well adapts itself to such a paging receiver with respect to size and service life and, especially, space requirement. However, it is impractical to use a manganese dry cell with a watch type paging receiver whose space is limited. While such a manganese dry cell may be replaced with a button type manganese cell, the latter cannot power a watch type paging receiver over a long period of time because of its small capacity. Should a longer power source life be desired, the battery would become greater in size than the receiver body.